Long-term cultures of epithelial-like cells were initiated from African green monkey and canine tracheobronchial tissue explants. Characterization studies are now in progress. Cell hybridization procedures are being used to produce hybridomas which synthesize antibodies against mucus-producing and other tracheobronchial epithelial cells. Attempts to develop cultures of functional mucus-producing cells are being made using cell fusion and viral transformation techniques. The attachment and growth of cells from enzymatically-dissociated canine tracheobronchial tissue was shown to be promoted by fetal bovine serum. In the absence of serum some stimulation was noted in culture vessels pretreated with type 1 collagen. Laminin and fibronectin alone or in combination with collagen appeared to have no effect. A similar effect of serum was observed in enzymatically-dissociated African green monkey tracheobronchial tissue. Irradiated lung fibroblast feeder cells had a stimulatory effect both in the absence and presence of serum. The mitogens Con A phytohaemagglutinin, and pokeweed mitogen did not promote cell growth or survival in culture. Further studies of factors on cell attachment, growth and function are in progress. The mechanism of action of the stimulatory effects of serum and feeder cells is being investigated.